Ceramic matrix composites (CMCs) are composite materials consisting of a ceramic matrix having reinforcement materials (e.g., particulates, whiskers, non-woven fibers, woven fibers) embedded therein. CMCs are attractive materials for use in aerospace applications because they are relatively lightweight and are able to sustain high operating temperatures. For example, CMCs may be beneficial for the construction of exhaust system components because they are lighter in weight and are able to sustain longer exposures to exhaust temperatures than some metal-based structures (e.g., titanium and nickel-based alloys) used currently.
CMC sandwich structures, which include a load-transferring core bonded to and between two identical facesheets, have been explored as exhaust components for aircraft applications (see U.S. Patent Application Publication Number 2009/0004425). While effective, CMC sandwich components may be subjected to stresses when a high thermal gradient exists across the sandwich structure, particularly when the facesheets are constrained, such as in a cylindrical sandwich structure. Specifically, the facesheet that is exposed to a higher temperature environment (the ‘hotter facesheet’) expands or tries to expand, but is resisted by the opposing facesheet that is exposed a cooler environment (the ‘cooler facesheet’). As a result, the hotter facesheet may be subjected to compression stress due to the expansion resistance of the cooler facesheet, while the cooler facesheet may be subjected to tension stress caused by the contraction resistance of the hotter facesheet. Under some extreme conditions, such competing forces may push the CMC sandwich component to its structural limits, and structural damage may occur.
Thus, there are challenges and limitations of existing art that are to be overcome. In particular, there is a need for more robust CMC sandwich structure designs with improved resilience under thermal gradient conditions.